For the protection of persons and of the installation, medium-voltage switchgear assemblies are provided with apparatuses for releasing pressure in order for it to be possible for the hot gases produced in the event of an arc flashover to be dissipated safety from the installation area. A number of functional modules are usually used for these switchgear assemblies, the functional modules being encapsulated with respect to one another and with respect to the atmosphere such that the effects of an explosion in the interior of the functional module cannot spread to the area surrounding the installation. In the event of an arc forming in one of these functional modules, the excess pressure produced by the air suddenly being heated and the hot gases are dissipated such that neither persons nor the installation are harmed or damaged in any way. Pressure release ducts are usually provided for this purpose and are connected to the individual functional modules by means of a suitable valve system such that it is possible for the excess pressure and the hot gases to be dissipated from the affected functional module but at the same time such that it is not possible for the hot gases or a pressure wave to enter the other functional modules.
DE 31 25 364 A1 describes a pressure release duct which is rectangular in cross section and in whose interior the hot gases are first cooled by swirling and the excess pressure is reduced. Then, the gases are dissipated from the installation via ventilation slots such that they are thereafter only slightly harmful.
In DE 195 20 698 A1 and DE 196 45 304 C1, the pressure and temperature are reduced using so-called damping elements, in the form of cartridges, which are installed either within the installation or externally. The gases are in this case directed away either via ventilation slots into the area of the building surrounding the installation or to the outside via a chimney system.
With all of these solutions it is possible, however, for the pressure release duct having a rectangular cross section not to be suitable for loads in the case of particularly intensive arc flashovers.